1. 03/20121 Back to Basics, 2012 POPULATION HEALTH: Infectious Diseases and Outbreak Investigation N. Birkett, MD Epidemiology & Community Medicine Other resources available on Individual & Population Health web siteIndividual & Population Health web site

2. 03/20122 78-5 Outbreak Management (1) Physicians are crucial participants in the control of outbreaks of disease. They must be able to diagnose cases, recognize outbreaks, report these to public health authorities and work with authorities to limit the spread of the outbreak. A common example includes physicians working in nursing homes and being asked to assist in the control of an outbreak of influenza or diarrhoea. Key Objectives Know the defining characteristics of an outbreak and how to recognize one when it occurs. Demonstrate essential skills involved in controlling an outbreak and its impact on the public, in collaboration with public health authorities as appropriate.

3. 03/20123 78-5 Outbreak Management (2) Enabling Objectives Define an outbreak in terms of an excessive number of cases beyond that usually expected. Describe and understand the main steps in outbreak management and prevention. Demonstrate skills in effective outbreak management including infection control when the outbreak is due to an infectious agent. Describe the different types of infection control practices and justify which type is most appropriately implemented for different outbreak conditions. Demonstrate effective communication skills with patients and the community as a whole. Describe appropriate approaches to prevent or reduce the risk of the outbreak recurring.

4. 03/20124 Infectious Disease Summary Terminology Nature of diseases Outbreaks/epidemics –Identification –Methods of control

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6. 6 Foodborne Botulism Clostridium perfringens Hepatitis A Norovirus Salmonellosis Shigellosis Staphylococcal disease Trichinosis Water & Foodborne Amebiasis Cholera Giardiasis Legionellosis E coli Person-to-person spread Aseptic meningitis Hepatitis B and C Respiratory Infections (e.g., influenza) Herpes simplex Streptococcal disease Tuberculosis Leprosy Infections: Sources and agents (1)

7. 03/20127 Arthropod Borne Encephalitis (West Nile) Lyme Disease Malaria Plague Rocky Mountain Spotted Fever Sexually Transmitted HIV/AIDS Gonorrhea Syphilis Chlamydia trachomatis Vaccine preventable Chickenpox Diphtheria, pertussis, tetanus Hepatitis A and B HPV Influenza Measles, mumps, rubella Meningococcal Pneumococcal Poliomyelitis Infections: Sources and agents (2) Zoonotic Psittacosis Q fever Rabies Hantavirus West Nile Fungal Candidiasis Coccidioidomycosis Histoplasmosis Prions Kuru vCJD

8. 03/20128 Terminology (1) Infectivity –The ability of an agent to invade and multiply in a host (an infection). –Dose of organism required to establish infection in 50% of animals. Pathogenicity –The ability of an agent to produce clinically apparent illness.

9. 03/20129 Terminology (2) Virulence –The proportion of clinical cases which produce severe disease and/or permanent sequelae. Immunogenicity –The ability of an agent to produce specific immunity against the agent –Can be produced in general body or within specific sites such as the GI tract. –Determines the ability of an agent to re-infect the same host e.g., measles vs. gonorrhea

10. 03/201210 Terminology (3) Reservoir –Living organisms or inanimate matter in which infectious agent normally lives and multiplies Fomites (Vehicle) –Inanimate objects contaminated with infectious agent (not the reservoir). E.g. toys in a daycare centre. Vector –An animate source of an infectious agent. The vector may be infected with the organism (e.g. mosquitoes and malaria) or just be a mechanical carrier (e.g. flies). There is disagreement about whether vectors are restricted to insects or can also include small mammals such as rodents.

11. 03/201211 Terminology (4) Zoonoses –Diseases transmitted to humans from animals (e.g. anthrax) Carriers –An infected person without apparent clinical disease who remains infectious (e.g. Typhoid Mary) Index Case –The first case to be diagnosed in an outbreak –Sometimes defined as the first case noticed in the outbreak Contacts –People who have possibly been infected due to relevant contact with an infectious case

12. 03/201212 Terminology (5) Attack Rate –The probability that people will get ill from the disease. Usually applied in an outbreak situation. Secondary Attack Rate –Probability of infection in a closed group who are at risk but excluding the index case(s). Formula is:

13. 03/201213 Terminology (6) Case Fatality Rate (CFR) –The probability of death in people with an infection.

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17. 03/201217 Pathogenic Mechanisms (1) Direct Tissue Invasion (Group A Strep) Production of Toxins (Diphtheria) Allergic Host Reaction Resistant/latent infection (carriers) Enhancement of host susceptibility to drugs (e.g. Reye’s syndrome and ASA). Immune Suppression

18. 03/201218 Reservoirs (examples of transmission patterns) HumanHumanHuman AnimalAnimalAnimal Human Vector Animal Vector Human

19. 03/201219 Mechanisms of Spread (1)Spread Touch (many URI’s, scabies) Bite (rabies) Kiss (mononucleosis) Sexual contact (Chlamydia) Droplet, over 5 u, spread 1-2 meters (resp. virus) Soil (tetanus) Transplacental (hepatitis B) Vehicle borne (inanimate) fomites (e.g. toys) Food IV fluid organism may or may not multiply E. coli in hamburger Vector borne (animate) mechanical (e.g. soiled feet of insect) biological (e.g. malaria) Direct transmission Indirect transmission

20. 03/201220 Mechanisms of Spread (2)Spread Airborne transmission Droplet nuclei –tuberculosis, –measles, –varicella, –smallpox, –? Influenza) Dust –anthrax Mechanisms of Spread (2)Spread

21. 03/201221 Epidemics (1) Epidemic (now often called an ‘outbreak’, especially if localized) –the occurrence in a community or region of cases of a disease/condition/behaviour clearly in excess of normal expectancy Endemic –the occurrence of a disease/condition at a relatively constant level in a given setting, usually with on-going transmission Pandemic –an epidemic covering a very wide area and affecting a large proportion of the population (SIM web link)SIM web link Pathogen –Infectious and non-infectious substances capable of producing tissue damage or initiating a process which can lead to a disease.

22. 03/201222 Epidemics (2) Common conditions increasing likelihood of an epidemic –The introduction of a new pathogen or an increased amount of, or a change in the virulence of, a pathogen. –An adequate number of exposed and susceptible persons. –An effective means of transmission between the source of the pathogen and the susceptible person.

23. 03/201223 Epidemics (3) Incubation period and causal agent Time frameExamples HoursFood toxins Heavy metals DaysBacterial infections Salmonella / cholera WeeksMeasles / mumps / Hep A MonthsHep B / Rabies YearsKuru / cancer

24. 03/201224 Epidemics (4) Types of epidemics –Common source Point source Ongoing exposure Need not be geographically localized –Propagated/progressive –Mixed Epidemic curve Spot maps Note that epidemics can arise from behaviour as well as from traditional infectious sources.

25. 03/201225 Epidemic Curves: point source (1)

26. 03/201226 Epidemic Curves: propagated (2) 10 days

27. 03/201227 Exposure Maximum incubation period Average incubation period Minimum incubation period Distribution of cases by onset of symptoms: point source type

28. 03/201228 Exposure begins & continues

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30. 03/201230 Factors Influencing Spread of Disease in a Population (1) Period of infectivity in relationship to symptoms –Includes consideration of carrier states Herd immunity Type of spread –Direct –Indirect –Airborne Transmission mechanics –Consider sexual vs. droplet spread

31. 03/201231 1.No virus circulating in animals has caused human disease 2.Animal virus has caused disease in humans 3.Some human to human transmission but not enough to sustain community outbreak 5.Human to human spread in at least two countries of one WHO region 6.Phase 5 + a community level outbreak in at least one other WHO region Post peak period Incidence is decreasing although waves of increased incidence may occur 4.Sustained human to human transmission leading to community level outbreaks Post pandemic period Return to normal levels Time WHO Stages of a Pandemic

32. 03/201232 Develop disease Immune Herd Immunity

33. 03/201233 Epidemic Control (1) Twin goals: Minimize the impact to the affected community Understand the cause and mode of transmission Goals can conflict: Need to take action in absence of full information Need to collect full information base Effective and clear communication with general public is essential SARS outbreak designate one spokesperson regular press briefings

34. 03/201234 Actions for ‘acute’ outbreak control Isolation separation of infectious persons or animals from others during the period of communicability –usually isolate for at least two incubation periods. Quarantine restrictions on the activities of well people who (may) have been exposed to a communicable disease during its period of communicability. –active surveillance is an alternative –usually quarantine for the longest usual incubation period Often at least two incubation periods. –More controversial than isolation since it affects people who are not currently ill (and may never get ill). –we expect some who are quarantined to get sick Immunization passive or active Passive (IGG) can be more useful for acute outbreak control Chemoprophylaxis

35. 03/201235 General approaches to outbreak control (1) Reduce host susceptibility Immunization (active and passive) nutrition improved living conditions and other social determinants of health Interrupt transmission of the agent quarantine/isolation case treatment contract tracing inspections environmental clean-up animal population control –rabies vaccination of wild animals –insect spraying –monitor for animal infections

36. 03/201236 General approaches to outbreak control (2) Inactivate agent water purification; chlorination Personal hygiene measures hand hygiene (#1 strategy) cough etiquette protective clothing (masks, gowns) avoid at risk situations Family/community measures preventing sexual abuse of children leads to reduction in STIs Needle exchange and related programmes.

37. 03/201237 Surveillance The continuing scrutiny of all aspects of occurrence and spread of disease that we pertinent to effective control Reportable diseases.Reportable Sentinel practices Animal/water surveys Environmental monitoring Mortality (vital statistics) Provincial laboratory tests Epidemic investigations Disease registries CIHI and related data.

38. 03/201238 More MCQs Here are some more questions that students can use to test their own knowledge: http://www.medicine.uottawa.ca/sim/data/Se lf-test_Qs_Outbreaks_e.htm (The questions contain comments on the answers, to illustrate why a given response is not correct) Here are some more questions that students can use to test their own knowledge: http://www.medicine.uottawa.ca/sim/data/Sel f-test_Qs_Outbreaks_e.htm (The questions contain comments on the answers, to illustrate why a given response is not correct)

39. 03/201239 Distribution of cases by onset of symptoms. Intermittent outbreak Time

40. 03/201240 Index case Maximum incubation period Average incubation period Minimum incubation period Distribution of cases by onset date: Point source with index case and limited spread

41. 03/201241 Days Index case Average incubation period Distribution of cases by onset of symptoms. Point source, index case with propagated spread